The present invention relates to an automatic transmission control system and a method thereof that is capable of decreasing gear select shock generated when a shift lever is shifted.
Generally, in an automatic transmission of a vehicle, if a driver selects a desired range by moving a shift lever, a port of a manual valve changes so that a predetermined line pressure is generated by hydraulic oil supplied from an oil pump. This causes an transmission control unit to control of a plurality of solenoid valves, based on vehicle operating conditions such as vehicle speed and throttle position, in order to shift the automatic transmission into a desired gear.
For example, if the shift lever is positioned in drive (D) when the vehicle is stopped, line pressure is formed in shift control valves and a pressure control valve. A rear clutch is then engaged by generating line pressure through a N to D control valve to achieve a first speed.
If the shift lever is shifted into neutral (N) from drive (D) once the first speed has been achieved, line pressure in the shift control valves, the pressure control valve, and the rear clutch, is released regardless of any control. Output torque, which maintains the first speed, instantaneously disappears so that a gear select shock occurs. Such gear select shock is generally referred to as a D to N gear select shock.
The release of the hydraulic pressure which occurs just after shifting into neutral (N) from drive (D), is mainly determined by the structural characteristics of the automatic transmission, such as a mounting assembly of a valve body, a valve orifice, an accumulator spring, etc. Therefore, any control of the release of the hydraulic pressure is difficult.
To decrease the D to N gear select shock, methods have been developed to change the valve orifice and the spring coefficient of the accumulator spring. However, effects of such changes are relatively small, and they inevitably necessitate changes in the valve body, which has a complicated structure.
In a preferred embodiment of the present invention, the shift control system for decreasing gear select shock comprises a vehicle speed sensor, a throttle position sensor, an inhibitor switch, an idle switch, a controller, and an actuator. The vehicle speed sensor detects a vehicle speed. The throttle position sensor detects a throttle position. The inhibitor switch detects a position of a shift lever. The idle switch detects whether an engine is in an idle state. The actuator is controlled by the controller and shifts the automatic transmission into a specific gear. The controller controls the automatic transmission in order to decrease gear select shock generated when the shift lever is shifted into neutral from a drive range, and up-shifts the automatic transmission if a vehicle is stopped and idle conditions exist in the drive range.
In a further preferred embodiment of the present invention, the controller up-shifts the automatic transmission to a second speed gear from a first speed gear if a vehicle is stopped and idle conditions exist in the drive range.
In a further preferred embodiment of the present invention, the controller up-shifts the automatic transmission to a third speed gear from a first speed gear if a vehicle is stopped and idle conditions exist in the drive range.
In an alternative embodiment of the present invention, it is determined whether a vehicle is stopped and whether idle conditions exist based on vehicle operating parameters. It is then determined whether the vehicle has been stopped for longer than a predetermined period in an automatic forward drive range. The automatic transmission is then sifted to a higher speed gear from a first speed gear if it is determined that the vehicle has been stopped for longer than the predetermined period in the drive range. The automatic transmission is then shifted into neutral by applying pressure when a selection of a neutral range from the automatic forward drive range is detected. It is preferable that in the up-shifting step, the automatic transmission is shifted from a first speed gear to a second speed gear or a third speed gear.
In a further preferred embodiment of the present invention, the automatic transmission is down-shifted from the up-shifted speed gear to a first speed gear if an off signal of the idle switch is detected.
According to another embodiment of the invention, there is provided a shift control system for decreasing gear select shock in an automatic transmission. The shift control system includes a vehicle sensor, a throttle sensor, an inhibitor switch, an idle switch, a controller, and an actuator. The vehicle speed sensor is configured to detect a vehicle speed. The throttle position sensor is configured to detect a throttle position. The inhibitor switch is configured to detect a position of a shift lever. The idle switch is configured to detect whether an engine is in an idle state. The controller is coupled to the vehicle sensor, throttle sensor, inhibitor switch, idle switch, and actuator. The controller includes a memory including instructions for determining whether said vehicle is stopped, in a drive gear, and has been in an idle state for a predetermined period of time. The memory also includes instructions for shifting the automatic transmission into a higher drive gear than said drive gear, such that torque is reduced, thereby decreasing gear shift shock on a subsequent shift into neutral. The actuator is controlled by the controller for shifting the automatic transmission into a specific gear.